docs: Add tool discovery proposal

[rubambiza]

Summary

• Proposes optional, opt-in tool discovery for KAN: a controller that calls tools/list on MCP backends, validates schemas, and surfaces discovered tools in XBackend.status
• Enables policy validation against real backend state, operator visibility via kubectl, and a foundation for response filtering
• Discovery is advisory (does not affect policy enforcement) and opt-in via annotation

Phasing

• Phase 1: In-cluster discovery over plain HTTP with graceful failure for auth-required backends
• Phase 2: External backends with TLS/authentication (deferred pending Backend spec stabilization)
• Phase 3: AccessPolicy cross-referencing against discovered tools

Prior discussion

This proposal was initially drafted and reviewed on the fork PR (rubambiza#1) with feedback from @evaline-ju and @david-martin incorporated.

Test plan

• Community review of proposal content and API design
• Alignment on community consensus points (XBackend.status location, MCP client library, sync interval)

[netlify]

✅ Deploy Preview for kube-agentic-networking ready!

Name	Link
🔨 Latest commit	6a59a19
🔍 Latest deploy log	https://app.netlify.com/projects/kube-agentic-networking/deploys/69e99a98f65e37000802c668
😎 Deploy Preview	https://deploy-preview-227--kube-agentic-networking.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: rubambiza
Once this PR has been reviewed and has the lgtm label, please assign david-martin for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Hi @rubambiza. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Tip

We noticed you've done this a few times! Consider joining the org to skip this step and gain /lgtm and other bot rights. We recommend asking approvers on your previous PRs to sponsor you.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[evaline-ju]

/ok-to-test